i) Field of the Invention
The present invention relates to a method and apparatus for carrying out a surface treatment of a fabricated heat exchanger such as an evaporator for an air conditioner while the heat exchanger is carried on and moved by a continuous overhead conveyer of a power and free type, and more particularly to a continuous surface treating method and apparatus with an inline centrifugal separator for liquid draining or removal, built in a continuous conveyer line of a power and free type.
ii) Description of the Related Arts
It is already known that it is necessary to improve the hydrophilic property (water-attractive property) when a surface treatment of a heat exchanger is carried out, as disclosed in Japanese Patent Laid-Open No.Hei 1-314158 ("Heat Exchanger, Manufacture Thereof and Surface Treatment Agent Thereof") and No.Hei 3-26381 ("Aluminum Heat Exchanger and Its Producing Method"). In these prior arts, an antimicrobial agent or a water-soluble polymer is used for improving the hydrophilic property. However, in a heat exchanger W, as shown in FIG. 1, a spacing between two adjacent fins Wa is small and a liquid draining property is bad. Hence, it is unavoidable to admix a chemical conversion coating (chromating) liquid in a previous process into a hydrophilic coating liquid bath and a concentration of the hydrophilic coating liquid becomes uneven. Thus, a film thickness is not fixed and the quality is unstable. Further, even when there is no mixing of the chemical conversion coating liquid into the hydrophilic coating liquid, the liquid draining property of the hydrophilic coated film is bad and the film thickness becomes uneven. For example, as a water soluble hydrophilic coating or a hydrophilic coating, a composition comprising, specifically, (a) 0.3-6 weight % of polyvinyl pyrrolidone having a polymerization degree of 10-1000; (b) 1-10 weight % of polyvinyl alcohol having a saponification degree of 80% or more and a polymerization degree of 100-1000, a weight ratio of the component (a) to the component (b), (a)/[(a)+(b)], being in the range of 0.1-0.9; and (c) residual water to make 100% composition, is used.
As a method for improving the liquid draining property of bolts, nuts and the like treated in a surface treating line, a centrifugal separator can be used, as disclosed in Japanese Patent Laid-Open No.Sho 59-76557 ("Centrifugal Separation Device") and No.Sho 60-7950 ("Vessel and Process for Centrifugal Separation").
Conventionally, as a centrifugal separator, a basket or the like for containing objects to be treated is rotated by a motor or the like. After the objects attached with treating liquid in a previous process are put into the basket, the basket is rotated to carry out a centrifugal separation of the treating liquid and the objects with the liquid removed are taken out to sent to a next treating process. The treating liquid centrifugally separated from the objects is drained from the loopholes of the basket and is collected by a liquid collecting container fixed so as to surround the basket.
The mounting and demounting or putting and taking of the objects to be treated into and out of the centrifugal separator require a lot of time and effort. In particular, in the case of a large number of small objects to be treated, this replacing work requires an extreme amount of time and effort and remarkably reduces workability of not only the centrifugal separating process but also the whole treating line.
On the other hand, as a conveying means of the objects to be treated in various treating lines, a continuous trolley conveyer system is used. In this continuous conveyer, chains and the like run on a ceiling of a factory and the objects to be treated are directly carried on hangers hung from the running chains or vessels containing the objects are carried on the hangers so as to convey the objects.
In order to perform the aforementioned "liquid draining or removal" in a treating line having such a continuous trolley conveyor system, the excessive treating liquid is naturally dropped from the objects, or by an air blow or a hot air blow, the liquid removal is forcibly executed. However, by the natural dropping, the efficiency is extremely bad and perfect liquid draining can not be performed. Also, by the air blow or the like, a uniform liquid removal can not be carried out.